What are Mechanical Extract Ventilation Systems?

A Mechanical Extract Ventilation unit also known as MEV, (cMEV & DCV) is a ventilation system that extracts moisture laden air from multiple wet rooms in your home. MEV units provide a simultaneous, low level of extraction continuously 24/7.

Suitable for extract from rooms such as toilets, bathrooms, shower rooms, laundry rooms, en suites, kitchens, and utility rooms. A MEV system replaces your normal bathroom fans to a single, quieter, and more powerful fan installed in the roof space or cupboard and is suitable to extract in up to 6 wet rooms.

A MEV unit is also extremely popular for large bathrooms and commercial rooms requiring a very powerful and quiet extraction system.

Benefits of MEV

  • Can extract simultaneously from up to 6 wet rooms

  • Continuous operation

  • Prevents condensation & mould growth

  • No extractor fans needed

  • Quiet in operation

  • Low running cost

  • Humidity sensor models available

  • Wireless controlled models available

  • Acoustic lined models available

  • Low specific fan power

  • SAP Appendix Q rated

  • Manufactured in the UK

  • Up to 5-year warranty


Demand Control Ventilation (DCV) is not a single type of product but is the way a system is controlled, A DCV system will automatically increase performance depending on the air quality and this can be achieved in several ways including.

  • Humidity sensor at the unit

  • Co2 sensors

  • Humidity or PIR sensor in the room

  • Constant pressure fans

  • Automatic air valves

Constant Pressure

When a normal MEV unit registers high humidity or is switched to boost it will increase performance to all connected rooms.

Constant Pressure (CP) units have a pressure sensor that with the use of automatic flow control air valves allows the airflow to be controlled independently in each room.

This is a much more expensive option but can provide a small but sometimes required benefit in energy performance and reduction in noise.


A MEV system extracts air but will require either trickle vents or a positive ventilation unit to bring air into the property.

A mechanical ventilation heat recovery (MVHR) system both extracts and supplies filtered air and recovers up to 90% of the normally wasted heat reducing your heating bills and all the air if fully controllable.

According to Building Regulations Approved Document F, for whole-house continuous mechanical ventilation systems you are looking at a choice between System 3 Continuous Mechanical Extract Ventilation (MEV) or System 4 Continuous Mechanical Ventilation with Heat Recovery (MVHR).

MEV Installation

Suitable for any type of home MEV units have multiple installation options and can be installed on the wall, ceiling or in a loft.

The unit is connected via ductwork pipes to valves in each wet room in your home. The air is extracted through the valves and ductwork, back to the unit where it is then expelled outside, giving your home a better indoor air quality.

MEV systems are easy to install and can be done via DIY or by most competent people and tradesmen, alternatively we can install your system for you via our network of installers across the UK and Ireland.

Ducting Options

MEV units are available with either circular or rectangular connection points.

The MEV units with rectangular connections use PVC or Thermal 204x60 ductwork and are extremely popular for apartments and concrete ceilings.

The MEV units with circular connections have several options of

  • 125mm PVC Ducting

  • 125mm Thermal ducting

  • 125mm Insulated flexible ducting

  • 90mm radial ducting

  • 75mm radial ducting

The most popular and long-life solution option would be to install the unit in the attic space and simply take a 90mm crushproof radial duct to each bathroom etc.

MEV Units

We stock only the highest quality MEV units from worldwide leading brands including Vent Axia, Duco, Domus, Passivent and Xpelair.

The Vent Axia Multivent is our most popular mechanical extract ventilation unit (MEV) with circular connections  we sell due to high quality construction, reliability and controllability, there are three 125mm extraction points on the sides and one 125mm to the back for ease of installation.

Check out our video for the Vent Axia MVDC-MS unit.

The Domus CMX units our most popular units with rectangular connections

MEV Kits

MEV units can be purchased on their own or in a MEV Kit.

MEV kits are a complete system which include an MEV unit of your choice with various options of type of ductwork for up to 7 separate areas.

Our comprehensive DIY kits have everything you should require installing the system to building control regulations. Kits include the correct ducting, connectors, grilles, valves, and installation materials for your chosen MEV unit.

For more info or to purchase an MEV system call our team on 028 2827 5150 and one of our sales and technical teams will be able to help you. Alternatively you can purchase an MEV unit and kit online, check it out here.